Pacific-Australia Climate Change Science and Adaptation Planning Program Ninigo Group Admiralty Islands Mussau Is. Lorengau Kavieng South Pacific Ocean Vanimo New Hanover N Tabar Is. Bismark Sea e w I Lihir Group re Wewak Bismarck l a n Archipelago d Rabaul Karkar Witu Islands Long Island B Madang o Buka Is. Mount u Kundiawa Umboi Is. g Hagen Kimbe a Goroka i n i Arawa a n INDONESIA t Mendi r i v N e w B i Lae l l e Huon Gulf Solomon Sea Kerema Gulf of Papua Kiriwina Islands SOLOMON Daru Popondetta Woodlark Is. ISLANDS PORT d’Entrecasteaux Is. MORESBY L o AUSTRALIA Alotau A r u c h i s i p i a Coral Sea e d Conflict l a e g Group o Tagula Current and future climate of Papua New Guinea > Papua New Guinea National Weather Service > Australian Bureau of Meteorology > Commonwealth Scientific and Industrial Research Organisation (CSIRO) Papua New Guinea’s current climate Most of the rainfall in Port Moresby Temperature comes from the West Pacific Monsoon. Year-to-year variability The temperature of the ocean Large differences in temperature Papua New Guinea’s climate varies surrounding Papua New Guinea has a between the land and the ocean drive considerably from year to year due strong influence on average monthly the monsoon, and its seasonal arrival to the El Niño-Southern Oscillation. air temperatures. Changes in the usually brings a switch from very dry This is a natural climate pattern that temperature from season to season to very wet conditions. In the north of occurs across the tropical Pacific are small but more marked around Port the country rainfall is more consistent Ocean and affects weather around the Moresby than further to the north. year-round, although the peak in rainfall world. There are two extreme phases corresponds to the monsoon season. of the El Niño-Southern Oscillation: El Niño and La Niña. There is also a Rainfall Rainfall in the north of Papua New neutral phase. Generally in Papua New Guinea is also affected by the Papua New Guinea has a wet season Guinea El Niño years are usually drier Intertropical Convergence Zone and, from November to April and a dry than normal while La Niña events are to a lesser extent, the South Pacific season from May to October (Figure 1), usually wetter. La Niña-associated Convergence Zone. These bands but these seasons are only noticeably prolonged rainfall has led to flooding of heavy rainfall are caused by air different in Port Moresby, where about and landslides, whilst El Niño- rising over warm water where winds 78% of the yearly average rainfall associated droughts have also taken converge, resulting in thunderstorm comes in the wet season. Due to their their toll on Papua New Guinea. During activity. The South Pacific Convergence location in the West Pacific Warm Pool, El Niño events the monsoon season Zone extends across the South islands in the north of Papua New also starts later. The dry season at Port Pacific Ocean from the Solomon Guinea experience rain throughout the Moresby is cooler than normal in El Islands to east of the Cook Islands, year. As a result, Kavieng’s average Niño years and warmer than normal in whilst the Intertropical Convergence annual rainfall (3150 mm) is much La Niña years, while the wet season Zone lies across the Pacific just higher than Port Moresby’s (1190 mm). tends to be warmer and drier than north of the equator (Figure 2). normal during an El Niño event. Figure 1: Seasonal rainfall and temperature at Port Moresby and Kavieng. 2 Current and future climate of Papua New Guinea | Current climate N H o N 20 o Federated States of Micronesia Palau Marshall Islands o n e I n t e r t r o p i c a l C o n v e r g e n c e Z Kiribati 10 o W a Nauru 0 r m p Tra de W inds o o l S o Papua New Guinea u M o t h Tu valu n Solomon Islands S s o P o East Timor o n a c i f i c C o n v e Samoa r g Vanuatu Fiji e n Niue c e S 10 Z o o To nga Cook Islands n e S 20 H o 0 500 1,000 1,500 2,000 30 Kilometres o E E E E E E E W W W W o o o o o o o o o o o 0 0 0 0 0 0 0 0 0 0 0 180 11 12 13 14 15 16 17 17 16 15 14 Figure 2: Average positions of the major climate features in November to April. The arrows show near surface winds, the blue shading represents the bands of rainfall convergence zones, the dashed oval shows the West Pacific Warm Pool and H represents typical positions of moving high pressure systems. Tropical cyclones Tropical cyclones tend to affect southern Papua New Guinea between November and April. In the 42-year period between the 1969 and 2010 seasons, 64 tropical cyclones developed in or crossed into the Papua New Guinea Exclusive Economic Zone, an average of 15 cyclones per decade (Figure 3). The number of cyclones varies widely from year to year, with none in some seasons but up to six in others. Over this period cyclones occurred in El Niño, La Niña and neutral years. Figure 3: Number of tropical cyclones developing within and crossing the Papua New Guinea Exclusive Economic Zone per season. The 11-year moving average is in blue. 3 Current and future climate of Papua New Guinea | Current climate Wind-driven waves Wind-waves around Papua New Guinea are typically not large, with markedly different behaviour on the north and south coasts. Waves are seasonally influenced by the trade winds, the West Pacific Monsoon and the location of the Intertropical Convergence Zone. From year to year they vary with the El Niño–Southern Oscillation. On the south coast waves are predominantly directed from the south-east throughout the year, but display strong seasonal variability with the largest waves during June to August (Figure 4, top). On the northern coast waves are characterised by the variability of trade winds and monsoon systems with the largest waves occurring during from December to March (Figure 4, bottom). Taking weather observations, Papua New Guinea Weather Service. Figure 4: Annual cycle of wave height (grey) and wave direction (blue) at Port Moresby (top) and Kavieng (bottom) based on data from 1979– 2009. The shaded boxes represent one standard deviation around the monthly means, and the error bars indicate the 5–95% range, showing the year-to-year variability in wave climate. The direction from which the waves are travelling is shown (not the direction towards which they are travelling). 4 Current and future climate of Papua New Guinea | Current climate Papua New Guinea’s changing climate rate of rise may be partly related to Temperatures Rainfall varies from natural fluctuations that take place year have increased year to year to year or decade to decade caused by phenomena such as the El Niño- Annual mean temperatures at Port There are no clear trends in rainfall Southern Oscillation. This variation in Moresby have increased since over Papua New Guinea since 1945 sea level can be seen in Figure 7 which 1943 at the rate of 0.22ºC per (Figure 5). Over this period, there includes the tide gauge records since decade (Figure 5). Maximum annual has been substantial variation in 1966 and the satellite data since 1993. temperatures have increased at a rainfall from year to year. There has rate of 0.13°C per decade and been little change in extreme daily minimum annual temperatures have rainfall over the same period. Ocean acidification increased at 0.3ºC per decade. The has been increasing number of warm days and warm Sea level has risen nights has also increased since 1943 About one quarter of the carbon dioxide at both Port Moresby and Kavieng. As ocean water warms it expands emitted from human activities each Over the same period the number causing the sea level to rise. The year is absorbed by the oceans. As the of cool days and cool nights (Figure 6) melting of glaciers and ice sheets extra carbon dioxide reacts with sea has decreased. These temperature also contributes to sea-level rise. water it causes the ocean to become slightly more acidic. This impacts increases are consistent with the Instruments mounted on satellites and global pattern of warming. the growth of corals and organisms tide gauges are used to measure sea that construct their skeletons from level. Satellite data indicate the sea carbonate minerals. These species are level has risen near Papua New Guinea critical to the balance of tropical reef by about 7 mm per year since 1993. ecosystems. Data show that since This is larger than the global average the 18th century the level of ocean of 2.8–3.6 mm per year. This higher acidification has been slowly increasing in Papua New Guinea’s waters. Papua New Guinea National Weather Service Papua New Guinea National Weather A coastal village near Port Moresby completely destroyed by Tropical Cyclone Justin in 1992. 5 Current and future climate of Papua New Guinea | Changing climate Figure 5: Annual average air temperature (red dots and line) and total rainfall (bars) at Port Moresby. Light blue, dark blue and grey bars indicate El Niño, La Niña and neutral years respectively.